The present invention generally relates to the field of providing a portable communication unit with a predetermined ID (identification) code to enable it to communicate with a base communication unit having a corresponding ID code. Examples of such apparatus comprise portable telephone systems, garage door openers and remote computer terminals which communicate with a master computer. In all of these situations desired communication between portable and base units is initiated only when correspondence exists between portable and base ID codes which are stored within the portable and base units, respectively.
In prior communications systems such as those mentioned above, typically the base and portable units are hardwire programed with their specific ID codes to enable them, for security purposes, to effectively communicate only with apparatus having the proper corresponding ID code. This hardwire programing can comprise either inserting a predetermined code plug in each unit, selectively making or breaking electrical connections within the base or portable unit, or providing the base and portable units with fixed electrical connections defining the desired ID code or codes. These prior systems generally result in requiring the pairing of the base and portable units once they have been coded, and this may be undesirable in many instances since it would require the sale and/or shipment of corresponding sets of base and portable units rather than the sale or shipment of individual base and portable units. While in some prior systems it is possible for the end user to manually enter (program) ID codes into the base or portable units, typically this step is time consuming and undesirable from the standpoint of the end use customer since it requires additional effort on his part. Also, typically only a relatively few codes can be manually selected by the end user, or else the cost of the manual programing apparatus or its complexity, and therefore its cost, must be greatly increased. If only a few codes are selectable by the end user, then the security of the communication system is jeopardized since others could accidentally or intentionally select the same codes.
Thus while prior systems have recognized that for security purposes it is desirable that the base and portable units only communicate with each other when they contain corresponding ID codes, prior systems have generally either provided hardwired ID codes to the base and portable units thereby necessitating the permanent pairing of the ID programed units, or they have provided for manual programing of the ID code of the base and/or portable unit thus requiring an undesirable manual operation for the end user as well as possibly jeopardizing the system security by providing only a relatively few codes.